1. Field of the Invention
The present invention relates to a device for simulating static load of a connection to at least one rack for animal cages when one or more of the racks are not connected to their respective supply or exhaust drops of a central ventilation system.
2. Related Art
Systems for providing air and removing exhaust from racks containing animal cages are known. U.S. Pat. No. 5,307,757 describes an animal cage rack including a forced air system in which positive air is supplied by an air inlet manifold. Air is removed from the cage by negative air pressure to an exhaust manifold. The exhausted air is treated with a laboratory air treatment system or portable HEPA filtered exhaust unit and is released.
Alternatively, air supply and exhaust for a rack of animal cages is supplied by a central ventilation system. Several racks can be connected to the ventilation system. The ventilation system includes an air supply drop and air exhaust drop. One end of the drop is connected to a respective duct of the ventilation system for either supplying air or removing exhaust. The other end of the drop is connected to a respective air supply plenum and air exhaust plenum of the rack of animal cages. This system has the disadvantage that when racks are removed from the drops the unattended exhaust drop or supply drop becomes the path of least resistance and a greater amount of air than originally intended follows this path, thereby bypassing the remaining racks.
Conventional control valves are used to control laboratory air flow of fame hoods having general exhaust and room supply air. The valves regulate air flow as duct static pressure varies. A pressure independent controller within the control valve adjusts to static pressure. For example, the controller can include a cone biased in a venturi to maintain a set flow. An example of this type of control valve is manufactured as an Accell(copyright)II Airflow Control Valve, by Phoenix Controls Corporation, Massachusetts. This type valve has the shortcoming of using a complicated mechanical system, which is expensive to manufacture and can be subject to mechanical failures.
It is desirable to provide a device for simulating static load of a connection to a rack of animal cages when one or more racks are not connected to the supply and exhaust of a central ventilation system in order to control air flow between the central ventilation system, thereby allowing the rack to be expeditiously removed from the ventilation system without impeding operation of the ventilation system.
The present invention relates to a device for simulating static load of a connection to a ventilated rack of animal cages when at least one of the racks are not connected to a central ventilation system. Accordingly, the device assures that the ventilation system is it, balanced when one or more of the ventilated racks are removed from their respective air supply or exhaust drops of the central ventilation system. The device includes a pair of spring biased legs which automatically close when a rack is removed from the central air system. The legs have an outwardly curved shape at one end forming an opening between the first and second leg. In the closed position, ends of the legs are adjacent to one another such that the distance between the legs is reduced, thereby creating a partial obstruction to air flow in the connection which is identical to the static load created by the ventilated rack. Preferably, a stop prevents the spring biased legs from overlapping in the closed position.
The spring biased legs include a handle at the other end. The legs can be opened by pressing the handle of each leg toward one another in order to increase the distance between the legs. In the open position, a plenum connection of a rack of animal cages can be inserted between the legs for connecting to a drop of the ventilation system. Accordingly, the plenum connection provides air supply and air exhaust to the rack of animal cages from a respective air supply drop or exhaust drop of the ventilation system.
A base ring is attached to the spring biased legs. An inner ring is attached to the base ring. The inner ring slides into the air supply or exhaust drops of the ventilation system. A band clamp ring couples the drops of the ventilation system to the base ring. Accordingly, the device is affixed to the air supply and exhaust drops of the central ventilation system and the device automatically simulates the static load when plenum connections to a rack of animal cages are removed from the central ventilation system.
The device can be color coded with a different color representing air supply and exhaust. The color coded device is attached to the respective duct of the ventilation system to aid identification of the air supply drop and exhaust drop. Accordingly, the device promotes expeditious connection of the respective air supply and exhaust plenums of the rack to a respective air supply drop and exhaust drop of the ventilation system.
The invention will be more fully described by reference to the following drawings.